When the glucose concentration in blood is measured, a method of using a disposable analysis tool is being employed as a simple and easy technique. The analysis tool includes, for example, an electrode-type biosensor 6 shown in FIG. 16 hereto (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 10-318969). The biosensor 6 is configured such that a response electric current value necessary to calculate a blood-sugar level is measured using electrodes 61 and 62 provided on a substrate 60. The electrodes 61 and 62 are covered by an insulating film 64 having an opening 64A, and the portions of the electrodes 61 and 62 exposed by the opening 64A constitute a reactive electrode 61A and an counter electrode 62A.
In the biosensor 6, the area of the reactive electrode 61A or the counter electrode 62A is controlled by the opening 64A of the insulating film 64. In other words, it is necessary to form the insulating film 64 using, for example, photolithography in order to control the area of the reactive electrode 61A or the counter electrode 62A. In addition, a deviation may be generated in the area of the reactive electrode 61A due to a deviation in the dimension of the opening 64A between plural glucose sensors 6. The reactive electrode 61A facilitates transfer of electrons from/to analysis target components, and a deviation in the area of the reactive electrode 61A generates a deviation in the sensitivity of the biosensor 6.
As a method of controlling an electrode area of the analysis tool, there is the following method as well.
In the chemical sensor electrode 7 shown in FIG. 17 hereto, a narrow-width neck section 71 extends from an electrode main body section 70, and the electrode main body section 70 is exposed by the opening 73 of the insulating film 72 (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2007-510902). The edge of the opening 73 in the insulating film 72 traverses the neck section 71. Therefore, even when the dimension of the opening 73 has a deviation, it is possible to suppress a deviation in the area of the electrode main body section 70.
The electrode strip 8 shown in FIG. 18 hereto has an reactive electrode 80 and a dummy electrode 81. The electrodes 80 and 81 are exposed by the opening 83 of the insulating film 82 (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-516038). In such an electrode strip 8, since the reactive electrode 80 and the dummy electrode 81 have an island shape, it is possible to prevent the deviation in the area of the reactive electrode 80 even when the deviation exists in the dimension of the opening 83.
On the contrary, in the chemical sensor electrode 7 or the electrode strip 8 shown in FIGS. 17 and 18, it is necessary to form the insulating films 72 and 82 using, for example, photolithography or the like in order to control the area of the electrode main body section 70 or the reactive electrode 80. Therefore, processes or equipments for manufacturing the analysis tools 7 and 8 become complicated, and manufacturing cost increases.
In the biosensor 9 shown in FIGS. 19A and 19B hereto, a slit 91 is formed in a metal film of the substrate 90, and the reactive electrode 93 and the counter electrode 94 are controlled by a pair of covers 92 (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 9-189675). In this biosensor 9, since the area of the reactive electrode 93 can be controlled without the insulating film, it is possible to advantageously make it easier to perform the manufacturing processes. On the other hand, since the area of the reactive electrode 93 depends on the accuracy of positioning or the shape of a pair of covers 92, it is difficult to accurately control the area of the reactive electrode 93.